Solvent Control of Electron Transfer Reactions

Raineri, Fernando O.; Friedman, H.

doi:10.1002/9780470141663.ch2

Cited by 46 publications

(34 citation statements)

References 229 publications

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“…Note that the frequency-dependent dielectric properties of a solvent also determine how fast and efficient it can respond to changes in the charge distribution of a solute, affecting thus fast photochemical and electron transfer reactions therein. 27,28 (p o 10 À8 bar) for 12 days at 40 1C. This reduced the water content to o100 ppm as measured by coulometric Karl Fischer titration.…”

Section: Introductionmentioning

confidence: 99%

Do H-bonds explain strong ion aggregation in ethylammonium nitrate + acetonitrile mixtures?

Sonnleitner

Nikitina

Nazet

et al. 2013

Phys. Chem. Chem. Phys.

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Binary mixtures of the protic ionic liquid ethylammonium nitrate (EAN) and acetonitrile (AN) were studied at 25 1C over the entire composition range by means of broadband dielectric spectroscopy covering 0.2 r n/GHz r 89. The dielectric spectra could be decomposed into two relaxation processes, both of which proved to be composite modes. For dilute solutions the higher-frequency Debye relaxation centered at B60 GHz is associated with the rotational diffusion of AN molecules, whereas at higher salt concentrations ultra-fast intermolecular vibrations and librations of EAN dominate the process. For EAN-rich solutions the lower-frequency relaxation is mainly due to jump reorientation of the ethylammonium cation, whereas contact ion pairs (CIPs) dominate this mode for dilute solutions. From the relaxation amplitudes effective solvation numbers and ion-pair concentrations were determined. For vanishing EAN mole fraction, x EAN -0, an effective cation solvation number of B7 was found which steeply drops until x EAN E 0.2 but shows only moderate decrease later on. The obtained association constant for EAN, K 0 A = 970 L mol À1 , exceeds that of other 1 : 1 electrolytes in AN by a factor of B30-50. This observation, as well as the fact that CIPs are formed despite strong cation solvation, indicates that ion pairing is mainly driven by the formation of strong hydrogen bonds between anions and cations.

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Section: Introductionmentioning

confidence: 99%

Do H-bonds explain strong ion aggregation in ethylammonium nitrate + acetonitrile mixtures?

Sonnleitner

Nikitina

Nazet

et al. 2013

Phys. Chem. Chem. Phys.

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“…Several simulation protocols in which polarization response is (partially) integrated out by analytical techniques have been proposed [20,21]. Integral equation theories have been successfully applied to small solutes [22], but examples of their application to solvation and reactivity of large solutes are just a few [23]. The formulation of the solvation problem in terms of molecular response functions holds significant promise, as it combines the molecular length scale of the polarization response with a possibility to accommodate an arbitrary shape of the solute [24,25,26,27,28,29,30,31,32,33,34].…”

Section: Introductionmentioning

confidence: 99%

Activation entropy of electron transfer reactions

2006

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We report microscopic calculations of free energies and entropies for intramolecular electron transfer reactions. The calculation algorithm combines the atomistic geometry and charge distribution of a molecular solute obtained from quantum calculations with the microscopic polarization response of a polar solvent expressed in terms of its polarization structure factors. The procedure is tested on a donor-acceptor complex in which ruthenium donor and cobalt acceptor sites are linked by a four-proline polypeptide. The reorganization energies and reaction energy gaps are calculated as a function of temperature by using structure factors obtained from our analytical procedure and from computer simulations. Good agreement between two procedures and with direct computer simulations of the reorganization energy is achieved. The microscopic algorithm is compared to the dielectric continuum calculations. We found that the strong dependence of the reorganization energy on the solvent refractive index predicted by continuum models is not supported by the microscopic theory. Also, the reorganization and overall solvation entropies are substantially larger in the microscopic theory compared to continuum models.

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“…(1) (2) resulting in the critical slowing down of the order parameter fluctuations. Transient grating optical Kerr studies 23 and dynamic light scattering 22 indeed reveal a slow relaxation time in the pretransitional region that follows the mean-field law, along with a temperature-independent relaxation associated with intradomain dynamics.…”

Section: Introductionmentioning

confidence: 99%

“…The main consequences of the effect of isotropic solvents on the activation barrier of ET are reasonably well understood. 1,2 The extension of ET theories into the realm of biological enzymatic and photosynthetic reactions 3 and molecular electronics 4 may require, however, the basic understanding of ET activation in anisotropic media characterized by a preferential direction of dipolar polarization. 5 Liquid crystals, in particular nematics, provide a model solvent for studying the effects of polarization anisotropy on electronic transitions in molecules.…”

Section: Introductionmentioning

confidence: 99%

Dynamical Arrest of Electron Transfer in Liquid Crystalline Solvents

Kapko

Matyushov

2006

J. Phys. Chem. B

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We argue that electron transfer reactions in slowly relaxing solvents proceed in the nonergodic regime, making the reaction activation barrier strongly dependent on the solvent dynamics. For typical dielectric relaxation times of polar nematics, electron transfer reactions in the subnanosecond time scale fall into nonergodic regime in which nuclear solvation energies entering the activation barrier are significantly lower than their thermodynamic values. The transition from isotropic to nematic phase results in weak discontinuities of the solvation energies at the transition point and the appearance of solvation anisotropy weakening with increasing solute size. The theory is applied to analyze experimental kinetic data for the electron transfer kinetics in the isotropic phase of 5CB liquid crystalline solvent. We predict that the energy gap law of electron transfer reactions in slowly relaxing solvents is characterized by regions of fast change of the rate at points where the reaction switches between the ergodic and nonergodic regimes. The dependence of the rate on the donoracceptor separation may also be affected in a way of producing low values for the exponential falloff parameter.

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Solvent Control of Electron Transfer Reactions

Cited by 46 publications

References 229 publications

Do H-bonds explain strong ion aggregation in ethylammonium nitrate + acetonitrile mixtures?

Do H-bonds explain strong ion aggregation in ethylammonium nitrate + acetonitrile mixtures?

Activation entropy of electron transfer reactions

Dynamical Arrest of Electron Transfer in Liquid Crystalline Solvents

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